Transactions of the Royal Scottish Society of Arts (Volume 2) (Abridged, Paperback, Abridged edition)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: On Trigonometrical Surveying and Levelling, and on the Effects of a Supposed Local Attraction at the Calton Hill. By WilLiam Galbraith, M.A., M.S.A., Edinburgh; F.R.A.S., London. (Read before the Society 14th December 1840.) In the course of some years past I have laid before the Society of Arts for Scotland a few remarks relative to the imperfect state of those usually reckoned our best maps of the country, and pointed out some instances of the amount of error. I also proposed formulae and rules to be observed in the practice of accurate trigonometrical surveying and levelling, which, in my opinion, might be easily understood and readily applied by any one possessing a moderate share of scientific knowledge. As a continuation of these, I shall, with permission of the Society, read the following few remarks on what has already been written, as well as on some connected observations which I have been enabled to make during the months of August and September last in the immediate vicinity of Edinburgh. I am gratified to find that the data on which the geodetical tables previously given were formed have been confirmed by a recent memoir of M. Bessel, the learned Astronomer of Koenigsberg, who had the benefit of the perusal of the results of several arcs of the meridian measured in Germany and Russia, communicated to him in manuscript, which were, consequently, unknown to me. It is fortunate, therefore, that M. Bessel's value of the radius of the equator deduced from these, combined with others formerly known, exceeds mine by 166 feet, and his value of the polar semi-axis exceeds mine by 334 feet only?small quantities in about twenty millions of feet. He also determines the most probable value of the French metre to be 443.321 French lines instead of 443.296 lines, that...